There is extensive art in this field.
U.S. Pat. No. 4,047,495 issued Sep. 13, 1997 to O'Brian Sep. 13, 1997, assigned to Polytop Corporation teaches a “snap top” child proof lid for a container. The patent teaches the living hinge is preferably injection molded from polypropylene because of the well-known living hinge properties of polypropylene. Other olefin polymers can be used but are not preferred (Col. 4 lines 41-50). The patent does not teach or suggest that the other polyolefins could be modified by radiation crosslinking to provide improved properties.
U.S. Pat. No. 4,638,916 issued Jan. 27, 1987 to Beck et al. assigned to Owens-Illinois, Inc., teaches a snap type hinge cap. The structural elements of the lid are disclosed but there is no disclosure of what material the lid may be made from. One of ordinary skill in the art would likely select polypropylene as the preferred material. Further there is no suggestion to use radiation crosslinking to improve the properties of the hinge.
U.S. Pat. No. 5,148,912 issued Sep. 22, 1992 to Nozawa et al., assigned to Yoshino Kogyosho Co., Ltd., teaches a slightly different snap top lid in which there are two separate hinges or straps. Again there is no disclosure of what material the lid may be made from. One of ordinary skill in the art would likely select polypropylene as the preferred material. Further there is no suggestion to use radiation crosslinking to improve the properties of the hinge.
U.S. Pat. No. 6,041,477 issued Mar. 28, 2000 to Rentsch et al., also teaches the structural elements of a snap top lid which differ from the prior art. While the patent contains a warning about residual stress in snap top lids having adverse effects on injection moulding plastic material, (Col. 3 lines 28 to 35), nowhere in the specification is there a disclosure of suitable materials from which to make the hinge. Further there is no suggestion to use radiation crosslinking to improve the properties of the hinge.
U.S. Pat. No. 6,766,926 issued Jul. 27, 2004 to Elchert assigned to Owens-Illinois Closure Inc., teaches the type of closure most commonly seen to-day. The structural elements of the cap are clearly disclosed. However, again the material form which the cap may be made is not discussed. Further there is no suggestion to use radiation crosslinking to improve the properties of the hinge.
Crosslinked polyethylene (PEX) is well known. Some applications it is used in include pipe and wire and cable coating. U.S. Pat. No. 8,192,813 issued Jun. 5, 2012 to Runyan et al., assigned to ExxonMobil Chemical Patents, Inc. and Zurn Pex, Inc. teaches modifiers which may be added to polyethylene to improve the properties of cross linked polyethylene. The present invention does not contemplate the use of additives to enhance the crosslinking, particularly in view of the fact that many living hinges are used in food dispensing containers. Interestingly the 813 patent does not teach or suggest using the crosslinked polyethylene in snap tops or living hinges.
The present invention seeks to provide a durable electron beam cross linked polyethylene web suitable for use in a hinge for containers.